Method of treating oils



Dec. 26, 1939.

D. L. HOQKER ET A1.

METHOD 0F TREATING OILS Filed April 50. 1957 PRAFF//V/C JOLI/770A( Patented Dee'. ze, 1939 PATENT OFFICE aisesss METHOD F TREATING OILS Douglas L. Hooker, Woodbury, N. J., and Carl M.

Fabian, Beaumont, Tex.,.assignors to Socony- Vacuum Oil Company,

Incorporated, New

York, N. Y., a corporation of New York Application April 30,'1937, Serial No. 139,836

4 Claims. (Cl. 196-13) This invention is directed to methods of solvent refining mineral oils to produce therefrom lubricant oil fractions of high viscosity index and low viscosity gravity constant (v. g. c.). Solvent re- 5A ning is a process wherein an oil is admixed with some liquid capable of exercising preferential solvent power for one of the groups of constituents in the oil, followed Aby phase separation, followed Y by removal of the solvent and the extracted constituent group admixed therewith. Double solvent rening is that variation of the above process wherein two solvents are employed, one exhibiting preferential solvent power for the parafnic constituents of low v. g. c., and-the other exhibiting preferential solvent; power for the naphthenic or aromatic constituents of high v. g. c. These two solvents are usually'allowed to flow countercurrently through a series of mixing andsettling stages, the oil to be treated bemg introduced at some stage intermediatev in the series. This. invention is concerned with the operation of such a treating system. A solvent reagent commonly used for naphthenrc solvent is tar acid, a mixture preponderatngt in cresylicV acid, known commercially as seec o. propane in liquid form or mixtures of similar light hydrocarbons, commercially termed "pro pane".

'I o properly understand not only the reasons giving rise to this invention, but the invention itself, reference is now made to the drawing attached to this specification, the single ligure of which shows an extractive apparatus suitable for commercial practice of the double solvent rening process and'of this invention as applied thereto. V

Referring to the drawing, the method of operation is as follows: Raw oil to be treated, stored 4o in tank 5, passed through pipe 6 to` mixer 1, where it is mixed with materials later described, thence through cooler 8 and pipe Sto enter chamber C of extractor III. Extractors III and II are composed respectively of successive chambers A, B,` C, D, and E, F, G, H, I, and may be separate as shown, or combined in one body. Eachv chamber is a settling space wherein Yphase separation may occur between the ramnate phase, composed of parafnic oil plus paralnic solvent, and the extract phase composed of naphthenic oil andnaphthenic solvent. Naphthenic solvent, hereinafter spoken of as selecto, usually a mixture of cresyllc and similar tar acids, originates in tank I2, and passes through pipe I3 to venter chamber I, wherein, after contact with oil, it be- The parafiinic solvent commonly used is comes extract. Thereafter, the extract moves through the settling chambers in reverse order, bing withdrawn from each chamber by a pipe I4, in which there is a pump I5, and introduced into the preceding chamber as the jetting medium ina jet mixing device I6 which is so mounted as to entrain rafnate layer from the preceding chamber. The only variants from this setup are in chamber I where the jetis fed by pipe. I3, between chambers B and C where the jet mixer .ing the same function as I6, and before chamber A, Where extract is pumped into pipe Il. The

paraflinic solvent, usually liquid propane, and

hereinafter referred to as propane, originates in tank I8, and passes'through pipe I1 to enter chamber A, where, after contacting with andA saparating from extract, it becomes known as railiinate, which rainate proceeds through chamber A to I in order by means of mixers I6 and pipes I9 and 20. In the operation thus described, the oil introduced at 6 is separated into a parafnic rafinate phase containing propane ,and some -selector which emerges from the extraction system by pipe 2 I and a naphthenic extract phase containing selector and some propane which emerges by pipe 22.

It will be seen from theabove that under normal conditions of operating, a constant amount of oil is introduced at pipe 9, a constant amount of selecto at pipe I3, and a constant amount of propane at pipe Il. It will also be noted that the supply of reagent to any stage consisting of a mixer and settler is dependent upon the ability of the stage preceding in the use of that reagent to reject the reagent. Thus the supply of paraffinic solvent in stage D, for example, isdependent upon the amount of propane plusparainic oilcommonly referred to as raflinate'fseparated in C, while the supply of naphthenic solvent in D is dependent .upon the amount of selecto plus naphthenic oil,-common ly referred to as extractseparated in E. In commercial operation of such a system, at high rates of separation it has developed that the solvent requirements at the various stages are not the same, more solvent being required in some stages than in others. This might be solved by the introduction of more fresh solvent to a particular stage except for the fact that stages'of treatment requiring high ratios are adjacent stages requiring low ratios, and both are intermediate between stages requiring intermediate ratios.

is replacedA by an external mixer to permit ofA lIhe object of this invention is to provide a method of operating a double solvent rening sys-4 tem to provide control over the ratios of solvents present in intermediate stages of the system and to permit individual variation of such ratios while maintaining a constant overall throughput of solvent.

.For an example of the method and its application, referring again to the drawing, the operation conducted in chambers A and B requires a relatively high ratio of paraiiinic solvent. The operation in chambers C and D requires a lower ratio of solvent, and the operation in chambers E and F requires a higher proportion of solvent to paraninic oil than would be the case if the rainate introduced to these chambers were the railinate produced by ilowing the whole of the propane used in chambers A and B through chambers C and D and then into E and F. demand may be met and the diioulty corrected by installing pipe 23, valve 2d in pipe i9 and valve 25 in pipe 23. Then the ramnate layer produced in chamber A, which is comparatively rich in parainic solvent and poor in parafnnic oil may be divided, less being introduced into chambers 2B, C, and D, and the remainder being introduced to chambers E, and F, or G. Thus the double advantage of treating in E and F with a solvent rich raninate is obtained, while at the same time the requirements of C and D are properly served. At the same time, it permits the amount of quality of solvent employed in chambers A, B, H, I to be the same, in proper accordance with their usual requirements. In commercial operation, this change has been found not only to permit of better and more constant operation at the same rate or throughput, but to enable the operation at higher rates of throughput for equal yield without derangement of operation.

We claim:

l. A method for double solvent rening oi. petroleum lubricant fractions, comprising the following steps': Flowing a parainnic solvent and a naphthenic solvent countercurrent through a series of stages each consisting of a mixing step and a settling step, introducing an oil to be treated to a stage intermediate the ends of the series, removing paraiiinic solvent and a railnate oil from one end of the series, removing naphthenic solvent and an extract oil from the other end of the series, and by-passing a portion of one solvent across at least one intermediate stage so thatthe throughput of solvent in that intermediate stage may be less than the total throughput, the throughput at the initial and end stages may be equal to the total throughput, and the relative concentration of solvent in the solvent-solute phase formed by the solvent at the point of rein- .troduction may be greater than in the absence oi such by-passing.

2. A method for double solvent rening of Thispetroleum lubricant fractions, comprising the iollowing steps: Flowing a paralnic solvent and a naphthenic solventV countercurrent through a series of stages each consisting of a mixing step and a settling step, introducing an oil to be treated to a stage intermediate the ends of the series, removing paraflinic solvent and a raiiinate oil together from one end of the series, removing naphthenic solvent and an extract oil together from the other end of the series, and by-passing a portion of the paraiinic solvent from a stage prior in order of parafilnic solvent ow to the stage where oil is introduced to a stage subsequent to oil introduction, whereby the throughput of that solvent at the stage of oil introduction is decreased, and the relative concentration of that solvent in the solvent-raffinate phase at the stage of reintroduction is increased, while the total throughput of that solvent remains constant and substantially equal in the initial and final zones in the direction of its flow.

3. 1n a duosol extraction process for separating a hydrocarbon oil into portions of different properties which comprises introducing a selective solvent for non-paraiiinic oil components into a o multi-stage countercurrent extraction apparatus at a nrst point, introducing auxiliary solvent for parainic components at a second point spaced from the rst, said auxiliary solvent and selective solvent being adapted to form two liquid phases when mixed with said oil under the conditions of the process, counteriiowing said solvents in the apparatus, introducing said hydrocarbon oil into the counterflowing solvents at a third point intern mediate said rst and second points, and removing said counterilowing solvents containing dissolved oil components at spaced points on either side of said third point, the improvement whichA comprises increasing the capacity of said apparatus by withdrawing a portion of the auxiliary solvent phase from a stage near said second point and introducing it into a non-adjacent stage in the direction of ilow of the auxiliary solvent pbase.

e. A method for double solvent reiining of petroleum lubricant fractions, comprising the iollowing steps: Flowing a paralnic solvent and a :naphthenic solvent countercurrent through a series of stages each consisting of a mixing step and a settling step, introducing an oil to be treated to a stage intermediate the ends of the series, removing parainic solvent and a ramnate oil together from one end of the series, removing naphthenic solventand an extract oil together from the other end oi the series, and by-passing a portion of the parainic solvent from a stage prior in order of parafnic solvent ow to the stage where oil is introduced to a stage subsequent to oil introduction. 1

' DOUGLAS L. HOOKER.

CARL M. FABIAN.

. f v cmmfrs oifcnmcnu, s

'l December '26, 1959.` DoUGLA'sJL. HOOKER', ET L.

It lsherfeby* certified that erro sposare inthe prltedsp'ecfichtio 'onclcoluzjmQlJ-.ne 2 0, forlsaparating' rfeal separating; lines 26 and 2 8, ffor ifsolectorh reed "selecto and that the said Letters Patent should be road with' this ,correctio therein that the same may` conform tothe record 'of the cese 'in the Patent Office.

:v sgged and sledthis 12th day of narn, A, D. 19m.

A. He-nryyaa; Arsdgle, (Segl) Acting ACcmmxissioner OIF-Patents. 

